SPID#: 3 During the past year, tests were conducted to determine behavioral andimmunological correlates of handedness in nonhuman primates. In one study, left-handed chimpanzees exhibited higher lymphocyte counts compared to right-handed chimpanzees over the course of a three-year assessment of immune response. In a second study, left-handed chimpanzees demonstrated greater avoidance behavior when presented with novel objects compared to right-handed subjects. Finally, a study was conducted on laterality and haptic discrimination in capuchin monkeys. A significant proportion of the subjects exhibited a preference to use their left hand when performing a haptic discrimination task compared to a simple reaching task. Several experiments were also conducted to examine the role of stimulus factors on the expression of cognitive asymmetries in chimpanzees. First, discrimination of compound visual stimuli on the basis of their global configuration or focal elements was examined in eight humans, six chimpanzees and seven monkeys. Overall, the humans performed significantly better than the chimpanzees, and the chimpanzees performed significantly better than the monkeys. For all three species, however, there was an effect for global precedence in the processing of compound stimuli. Thus, performance was significantly better on trials in which stimuli differed on the basis of global configuration compared to focal elements. Preliminary analyses on the chimpanzee data also suggest that discrimination on the basis on the local elements was performed better by the right hemisphere. In a series of experiments, six chimpanzees were tested for lateralization of function in categorical discrimination. A significant left-hemisphere advantage was found for both types of discrimination, but lateralization was much greater for the between-class discrimination. The results suggest that the biological basis of language may be present in nonhuman primates.